Heteromorphic polymer compositions

Abstract

The subject invention pertains to heteromorphic polymer compositions characterized as comprising: (a) a homogeneous linear or substantially linear ethylene/α-olefin interpolymer backbone; and (b) a branch appending from the backbone, which branch comprises an ethylene homopolymer or ethylene/α-olefin interpolymer having a density which is at least 0.004 g/cm 3 greater than that of the backbone. At least one of the backbone polymer or the branch polymer may be optionally functionalized to promote adhesion to polar surfaces. The heteromorphic polymer compositions of the invention exhibit enhanced upper service temperature. Also disclosed is a process for preparing the heteromorphic polymer compositions of the invention.

What is claimed is:  
     
       1. A heteromorphic polymer composition comprising the reaction product of: (a) a homogeneous linear or substantially linear ethylene/α-olefin interpolymer backbone polymer having a density of at least 0.850 g/cm 3  and of less than 0.920 g/cm 3 ; and (b) a branch appending from the backbone, which branch comprises an ethylene homopolymer or ethylene/α-olefin interpolymer having a density which is at least 0.004 g/cm 3  greater than that of the backbone. 
     
     
       2. The heteromorphic polymer composition of claim  1 , wherein the branch is characterized as comprising an ethylene homopolymer or ethylene/α-olefin interpolymer having a density which is at least 0.006 g/cm 3  greater than that of the backbone. 
     
     
       3. The heteromorphic polymer composition of claim  1 , wherein the polymer backbone is further characterized as a homogeneous linear or substantially linear interpolymer of ethylene and at least one C 3 -C 20  α-olefin. 
     
     
       4. The heteromorphic polymer composition of claim  3 , wherein the homogeneous linear or substantially linear interpolymer of the backbone is further characterized as having a CDBI of at least 50 and an M w /M n  of less than 3. 
     
     
       5. The heteromorphic polymer composition of claim  1 , wherein the interpolymer of the backbone is characterized as a substantially linear interpolymer characterized as having: 
       (a) a melt flow ratio, I 10 /I 2 ≧5.63,  
       (b) a molecular weight distribution, M w ,/M n  as determined by gel permeation chromatography and defined by the equation:  
       
         
           (M w /M n )≦(I 10 /I 2 )−4.63,  
         
       
       (c) a critical shear stress at the onset of gross melt fracture, as determined by gas extrusion rheometry, of greater than 4×10 6  dynes/cm 2  (0.4 MPa) or a gas extrusion rheology such that the critical shear rate at onset of surface melt fracture for the substantially linear ethylene interpolymer is at least 50 percent greater than the critical shear rate at the onset of surface melt fracture for a linear ethylene polymer, wherein the substantially linear ethylene interpolymer and the linear ethylene polymer comprise the same comonomer or comonomers, the linear ethylene polymer has an I 2 , M w /M n  and density within ten percent of the substantially linear ethylene interpolymer and wherein the respective critical shear rates of the substantially linear ethylene interpolymer and the linear ethylene polymer are measured at the same melt temperature using a gas extrusion rheometer, and  
       (d) a single differential scanning calorimetry, DSC, melting peak between −30 and 150° C.  
     
     
       6. The heteromorphic polymer composition of claim  1 , wherein the interpolymer of the backbone is characterized as a substantially linear ethylene/α-olefin interpolymer which is substituted with an average of 0.01 to 3 long chain branches/1000 carbons. 
     
     
       7. A heteromorphic polymer composition comprising a reacted product of (a) from 40 to 5 weight percent of a branch-forming polymer, which branch comprises an ethylene homopolymer or ethylene/α-olefin interpolymer, and (b) from 60 to 95 weight percent of a backbone-forming material which is ethylene and one or more comonomers or which is a homogeneous linear or substantially linear ethylene/α-olefin interpolymer; 
       wherein the crystallinity the resultant branch is at least 5 percent greater than the crystallinity of the resultant backbone; and  
       wherein the heteromorphic polymer composition has an upper service temperature which is at least 10° C. greater than a non-reacted blend of the polymer of the resultant branch and the polymer of the resultant backbone.  
     
     
       8. A heteromorphic polymer composition of claim  1 , further characterized as comprising moieties derived from the grafting of a polar moiety onto at least one of the backbone polymer or the branch polymer. 
     
     
       9. A heteromorphic polymer composition of claim  7 , further characterized as comprising moieties derived from the grafting of a polar moiety onto at least one of the backbone polymer or the branch polymer. 
     
     
       10. A process for preparing a heteromorphic polymer composition, wherein the process is characterized as comprising: 
       (a) polymerizing ethylene and optionally one or more α-olefin comonomers under reaction conditions to form a branch-forming polymer; and  
       (b) polymerizing ethylene, one or more α-olefin comonomers, and the branch-forming polymer of (a) under reaction conditions to form the heteromorphic polymer composition,  
       wherein the heteromorphic polymer composition is characterized as having a backbone polymer portion and an appending branch polymer portion, wherein the crystallinity at room temperature of the branch polymer portion is at least 5 percent greater than that of the backbone polymer portion.  
     
     
       11. The process of claim  10 , wherein the polymerizing of (a) occurs in a first reactor and the polymerizing of (b) occurs in a second reactor, or 
       wherein the polymerizing of (a) occurs in the same reactor as the polymerizing of (b), and wherein a first catalyst is employed during the polymerizing of (a) and a second compatible catalyst is employed during the polymerizing of (b).  
     
     
       12. A process for preparing a heteromorphic polymer composition, wherein the process is characterized as comprising: 
       (a) polymerizing ethylene and optionally one or more α-olefin comonomers under reaction conditions to form a reaction stream containing a branch-forming polymer;  
       (b) polymerizing ethylene and one or more α-olefin comonomers to form a reaction stream containing a homogeneous linear or substantially linear backbone-forming polymer,  
       (c) optionally isolating the branch-forming polymer from the reaction stream of (a) and the backbone-forming polymer from the reaction stream of (b), and  
       (d) reacting the branch-forming polymer and the backbone-forming polymer, in the presence of a free radical initiator, to append the branch-forming polymer to the backbone-forming polymer to produce the heteromorphic polymer composition;  
       wherein the branch-forming polymer has a crystallinity at room temperature which is at least 5 percent greater than that of the backbone-forming polymer.  
     
     
       13. The process of claim  12 , wherein the reacting of step (d) occurs prior to isolation of the branch-forming polymer and the backbone-forming polymer from the reaction streams of (a) and (b), and the process further comprises: 
       (e) isolating the heteromorphic polymer composition from the combined reaction stream.  
     
     
       14. The heteromorphic composition of claim  1  in the form of an adhesive, sealant, coating, molded part, film, thermoformed part, or fiber. 
     
     
       15. The hetermorphic composition of claim  14 , in the form of a hot melt adhesive formulation. 
     
     
       16. The heteromorphic composition of claim  15 , wherein the hot melt adhesive formulation is characterized as having a probe tack of at least 200 grams and an upper service temperature which is at least 10° C. greater than that of a hot melt adhesive comprising a non-reacted blend of the branch polymer and backbone polymer provided in equal amounts as is present in the heteromorphic polymer composition.